Woven ceramic filter bags or tubes have been shown to be effective collectors of particulates in high temperature environments. Conventionally, filter systems using such bags comprise a plurality of the bags each of which are mounted on a perforated metal support mandrel that is inwardly suspended from a wall of an enclosure, such as an insulated pressure vessel. As a flow of gases containing particulates is charged to the enclosure, the flow must pass through the suspended filter bags and is discharged through the mandrels which have an open end facing the outside of the enclosure. During the passage of the flow through the filter bags, the particulates are removed and collected on the surface of the bag that is exposed to the enclosure.
A major feature of the woven ceramic bag is its ability to be cleaned (i.e., the collected dust cake is dislodged from the filter and collected in a dust collection hopper) by reverse pulse jet methods. In a reverse pulse jet cleaning, a short, high pressure jet of gas, such as air, is fed to the interior of the perforated mandrel, through its open end, and the jet of gas imparts an expanding outward motion to the bag which dislodges the accumulated dust cake from the surface. The type of system above described and the jet pulse cleaning of filters in such a system are known.
In some instances, the flow of gas which contains the particulate material also contains vapor phase contaminants that pass through the filters and must be subsequently removed from the gas. For example, the conversion of fossil fuels to either combustion products or fuel gas can result in the release of particulate and gas phase contaminants such as alkali and sulfur to the gas stream. Utilization of the high temperature fuel or combustion gases requires the removal of both the particulate and gas phase contaminants to protect downstream equipment from corrosion and deposits and to meet environmental discharge regulations. New concepts are currently being developed that can removed particulates from high temperature gases and for removing alkali and sulfur. Most approaches to date have envisioned separate hardware arrangements for effecting the removal of each contaminant. These approaches generally result in expensive duplication of some hardware and the possibility of uneconomical systems.
It is an object of the present invention to provide a filter system which results in improved cleaning of filter bags.
It is another object of the present invention to provide a filter system that has a close coupling between a particulate separator and a fixed-bed contactor for the removal of vapor phase contaminants in a gas.